Immediate connection following device discovery

ABSTRACT

An electronic device is described. During operation, this electronic device activates a communication channel having a carrier frequency in a radio in an interface circuit to listen for an advertising frame of interest from another electronic device during a scan window having a predefined duration. If the advertising frame of interest is received from the other electronic device, the electronic device terminates the listening before the predefined duration has expired and, using the communication channel in the radio, transmits the connect request to the other electronic device to establish the connection with the other electronic device. In this way, the delay between discovery of the other electronic device and establishing the connection is reduced. In addition, the power consumed by the electronic device while scanning for the other electronic device and initiating the connection is reduced.

CROSS REFERENCE TO RELATED APPLICATIONS

The instant application is a continuation of, and hereby claims priorityto, pending U.S. patent application Ser. No. 14/542,161, which was filedon 14 Nov. 2014. The instant application also claims priority to U.S.patent application Ser. No. 13/627,913, which was filed on 26 Sep. 2012,which issued as U.S. Pat. No. 8,892,042 on 18 Nov. 2014, and of whichparent U.S. application Ser. No. 14/542,161 is a continuation. Theinstant application additionally claims priority to now-expired U.S.provisional patent application No. 61/657,363, which was filed on 8 Jun.2012, and to which parent U.S. application Ser. No. 14/542,161 andgrandparent U.S. application Ser. No. 13/627,913 claim priority. Each ofthese applications is incorporated by reference.

This application is related to U.S. Patent Application Ser. No.61/657,458, entitled “Duplicate Connection Detection for Devices UsingRandom Addresses,” by Augustin Prats and Joakim Linde, Attorney DocketNo. APL-P15345USP1, filed Jun. 8, 2012; U.S. Patent Application Ser. No.61/657,401, entitled “Caching of a Remote Data Structure Based onRequested Information,” by Augustin Prats, Jason C. Conn, Joakim Linde,and Brian J. Tucker, Attorney Docket No. APL-P15446USP1, filed Jun. 8,2012; and U.S. Patent Application Ser. No. 61/657,393, entitled“Identifying a Random Advertising Device as a Connected Device,” byJason C. Conn, and Augustin Prats, Attorney Docket No. APL-P15447USP1,filed Jun. 8, 2012, the contents of all of which are herein incorporatedby reference.

BACKGROUND

1. Field

The described embodiments relate to techniques for communicatinginformation between electronic devices.

2. Related Art

Many modern electronic devices include a networking subsystem that isused to wirelessly communicate with other electronic devices. Forexample, these electronic devices can include a networking subsystemwith a cellular network interface (UMTS, LTE, etc.), a wireless localarea network interface (e.g., a wireless network such as described inthe Institute of Electrical and Electronics Engineers (IEEE) standards802.11 or Bluetooth™ from the Bluetooth Special Interests Group ofKirkland, Wash.), and/or another type of wireless interface. In some ofthese electronic devices, the network interfaces can be used to detectother electronic devices as part of a process for enabling communicationbetween the electronic devices. For example, one electronic device canbroadcast an advertising frame which includes encoded information thatindicates a network address of the electronic device, and anotherelectronic device can monitor for the advertising frame to detect theelectronic device. Once the other electronic device detects or discoversthe electronic device, a connection protocol may be followed toestablish a connection between them.

However, there is typically a significant delay between discovery of theelectronic device and establishing the connection. For example,monitoring for the advertising frame by the other electronic deviceusually occurs during a scan window in a scanning operating mode. Evenif the advertising frame is received, the other electronic device maycontinue monitoring for additional advertising frames for a predefinedduration of the scanning operating mode or state. Then, the otherelectronic device may transition to an initiating (connecting) operatingmode or state, and may establish the connection. In addition toincreasing the time needed to establish the connection, this delay canalso increase power consumption, which is a problem in portableelectronic devices, such as battery-powered portable electronic devices.

SUMMARY

The described embodiments include an electronic device. This electronicdevice includes: an antenna; an interface circuit, coupled to theantenna, that communicates with other electronic devices; and controllogic coupled to the interface circuit. This control logic activates acommunication channel having a carrier frequency in a radio in theinterface circuit to listen for an advertising frame of interest fromanother electronic device during a scan window having a predefinedduration. If the advertising frame of interest is received from theother electronic device, the control logic terminates the listeningbefore the predefined duration has expired and, using the communicationchannel in the radio, transmits a connect request to the otherelectronic device to establish a connection with the other electronicdevice.

Note that the advertising frame may be of interest when a connection haspreviously been established with the other electronic device.

In some embodiments, the advertising frame includes an encoded address,and the control logic determines an actual address of the otherelectronic device.

Moreover, the communication between the electronic device and the otherelectronic device may use Bluetooth™. Furthermore, the connect requestmay be transmitted without waiting for an initiation state of theelectronic device.

Another embodiment provides an integrated circuit that includes theinterface circuit and the control logic.

Another embodiment provides a method for communicating betweenelectronic devices, which may be performed by the integrated circuit.During operation, the integrated circuit activates the communicationchannel having the carrier frequency in the radio in the interfacecircuit to listen for the advertising frame of interest from the otherelectronic device during the scan window having the predefined duration.If the advertising frame of interest is received from the otherelectronic device, the integrated circuit terminates the listeningbefore the predefined duration has expired and, using the communicationchannel in the radio, transmits the connect request to the otherelectronic device to establish the connection with the other electronicdevice.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flow diagram illustrating a method for communicating betweenelectronic devices in accordance with an embodiment of the presentdisclosure.

FIG. 2 is a flow diagram illustrating a method for communicating betweenelectronic devices in accordance with an embodiment of the presentdisclosure.

FIG. 3 is a flow diagram illustrating a method for communicating betweenelectronic devices in accordance with an embodiment of the presentdisclosure.

FIG. 4 is a flow diagram illustrating a method for communicating betweenelectronic devices in accordance with an embodiment of the presentdisclosure.

FIG. 5 is a timeline diagram illustrating scanning and initiation fortwo electronic devices in accordance with the described embodiments.

FIG. 6 is a flow diagram illustrating a method for communicating betweenelectronic devices in accordance with an embodiment of the presentdisclosure.

FIG. 7 is a flow diagram illustrating a method for communicating betweenelectronic devices in accordance with an embodiment of the presentdisclosure.

FIG. 8 is a block diagram illustrating a group of electronic deviceswirelessly communicating in accordance with an embodiment of the presentdisclosure.

FIG. 9 is a block diagram illustrating an electronic device inaccordance with an embodiment of the present disclosure.

FIG. 10 is a block diagram illustrating an integrated circuit inaccordance with an embodiment of the present disclosure.

Note that like reference numerals refer to corresponding partsthroughout the drawings. Moreover, multiple instances of the same partare designated by a common prefix separated from an instance number by adash.

DETAILED DESCRIPTION

FIG. 1 presents a flow diagram illustrating a method 100 forcommunicating between electronic devices, which may be performed byelectronic device 900 (FIG. 9) or integrated circuit 1000 (FIG. 10)(which may be included in electronic device 900 in FIG. 9). Duringoperation, the integrated circuit receives an advertising framecontaining an address (such as address P2) from another electronicdevice (operation 110). For example, the advertising frame may include aheader with a randomly generated (or pseudo-randomly generated) address(or network address) for the other electronic device. Using theBluetooth™ communication protocol as an illustration, the otherelectronic device may be peripheral and the electronic device (or theintegrated circuit) that receives the advertising frame while scanningmay be central. Moreover, the address may be generated by combining aportion of the Media Access Control (MAC) address of the otherelectronic device with a random number (i.e., a random number and asignature). In some embodiments, three bytes of the MAC address of theother electronic device are run through a hash function and combinedwith a random number. This combination may be encrypted, for example,using a 128-bit Advanced Encryption Standard (AES) encryption technique.

In order to offer privacy when advertising, the address included in theadvertising frames that are transmitted by the other electronic devicemay be periodically changed (for example, every 15 minutes). However, ifa connection was already established between the other electronic deviceand the electronic device (or the integrated circuit), then when theadvertising frame is received in operation 110, it may (erroneously)result in the other electronic device being detected or discovered as anew electronic device in the network. As a consequence, the electronicdevice (or the integrated circuit) may subsequently transmit a connectrequest and establish an (unnecessary) duplicate connection with theother electronic device.

To prevent this problem from occurring, the integrated circuitdetermines if a connection has already been established (operation 112)with the other electronic device using another address, such as aprevious version of the address (for example, other address P1) that wasgenerated with the aforementioned technique (and which may be differentfrom the address P2). In particular, the integrated circuit maydetermine the MAC addresses corresponding to the other address P1 and tothe address P2 to determine if they are the same. If so, instead ofestablishing another connection with the other electronic device usingthe address, the integrated circuit continues to use the connection withthe other electronic device using the other address (operation 114).

For example, if an application executing in an environment on theelectronic device tries to establish a connection with the otherelectronic device based on the ‘discovered’ address P2, the integratedcircuit may indicate to the application that a connection has alreadybeen established with the same electronic device at the other addressP1. To facilitate this, the integrated circuit may store information(such as a pointer) in a memory that relates the address P2 and theother address P1. In this way, two physical links to the same peripheralmay be prevented, thereby reducing power consumption and conservinglimited network resources.

However, if a connection has not already been established with the otherelectronic device using another address (operation 112), the integratedcircuit may establish a connection with the other electronic deviceusing the address (operation 116). Thus, if the MAC addressescorresponding to the other address P1 and to the address P2 aredifferent, or there is currently no connection between the electronicdevice and the other electronic device, a new connection may beestablished.

The operations in method 100 are further illustrated in FIG. 2. In thisfigure, time progresses from top to bottom.

In an alternative approach for dealing with the problem of duplicateconnections, the integrated circuit in the electronic device makes itappear as if the address P2 was never detected or discovered. Inparticular, when the other electronic device changes from the otheraddress P1 to the address P2, it first communicates this information(for example, in a payload of a packet) to the electronic device (or theintegrated circuit) using the other address P1 in the header of thepacket. After receiving this packet, the integrated circuit stores therelationship between the other address P1 and the address P2 (forexample, in a memory).

Subsequently, when frames or packets are received from the otherelectronic device with headers that include the address P2, theintegrated circuit modifies these frames or packets, replacing theaddress P2 with the address P1, so that it appears that the frames orpackets came from the other electronic device having the other addressP1. In this way, the application executing in the environment of theelectronic device may never know that the other electronic device wasdetected or discovered in the network at the address P2. This approachcan prevent confusion on the part of a user of the application. Notethat the modification of the packets may continue until the connectionbetween the electronic device and the other electronic device is brokenor reset.

This technique is shown in FIG. 3, which presents a flow diagramillustrating a method 300 for communicating between electronic devices,which may be performed by electronic device 900 (FIG. 9) or integratedcircuit 1000 (FIG. 10) (which may be included in electronic device 900in FIG. 9). During operation, the integrated circuit receives the packet(such as an advertising frame) containing the address (such as theaddress P2) from the other electronic device (operation 310). Then, theintegrated circuit determines if a connection has already beenestablished (operation 312) with the other electronic device using theother address, such as the other address P1. If so, the integratedcircuit modifies the packet by replacing the address with the otheraddress (operation 314) so that it appears as if the packet was receivedvia the connection with the other electronic device using the otheraddress. Otherwise, the integrated circuit leaves the packet unchanged(operation 316).

The operations in method 300 are further illustrated in FIG. 4. In thisfigure, time progresses from top to bottom. Note that, when advertisingframes with address P2 are received by the networking subsystem, theapplication in an upper software stack takes no action (i.e., does notinstruct the networking subsystem to establish a connection with theother electronic device at address P2) because the networking subsystemmodifies these advertising frames and replaces address P2 with addressP1.

In existing Bluetooth™ network interfaces, the electronic device (or theintegrated circuit) may have two distinct operating modes or states.During a scanning state, the electronic device listens for advertisingframes from other (unknown) electronic devices in a network (such as theother electronic device). In particular, during a scan interval, thereare scan windows when the electronic device listens for advertisingframes. If an advertising frame is received, at other times during thescan interval the electronic device may transmit a scan request torequest more information from the other electronic device.

Furthermore, in existing Bluetooth™ network interfaces, after apredefined duration of the scan interval (such as 110-120 ms), there isa separate initiating state, during which the electronic device canestablish a connection with a previously discovered electronic device,such as the other electronic device. For example, during the initiatingstate, the electronic device may listen for advertising frames. Ifanother advertising frame from the other electronic device is received(in addition to the advertising frame received during the scanningstate), the electronic device may transmit a connect request to theother electronic device.

However, because the scanning state typically has the predefinedduration, there is often a significant delay between when the otherelectronic device is discovered and when the connection is subsequentlyestablished. Moreover, because the interface circuit is activethroughout the scan time, the electronic device may also needlesslyconsume additional power.

Both of these problems can be addressed by merging the scanning stateand the initiating state into a common operating mode or state. Inparticular, when the electronic device receives an advertising framefrom the other electronic device when scanning or listening, theelectronic device may immediately determine if the discovered otherelectronic device is of interest (for example, if the electronic devicehas previously received an advertising frame from the other electronicdevice or has previously been connected to the other electronic device).If yes, without waiting for expiration of the predefined scan intervalor for the initiation state of the electronic device, the electronicdevice may transmit a connect request to establish a connection with theother electronic device. In this way, the time to connect may be reducedby more than a factor of two, with a commensurate reduction in powerconsumption.

This communication technique is shown in FIG. 5, which presents atimeline 500 illustrating scanning and initiation for two electronicdevices. When the electronic device receives advertising frame 510-2transmitted by the other electronic device, it determines that this isan advertising frame of interest based on the earlier receipt ofadvertising frame 510-1 transmitted by the other electronic device. As aconsequence, the electronic device switches its radio from receive totransmit, and transmits a connect request. Therefore, scan window 512-2is reduced in duration, as opposed to the normal predefined durationillustrated for scan window 512-1.

In addition, the communication technique is shown in FIG. 6, whichpresents a flow diagram illustrating a method 600 for communicatingbetween electronic devices. Note that method 600 may be performed byelectronic device 900 (FIG. 9) or integrated circuit 1000 (FIG. 10)(which may be included in electronic device 900 in FIG. 9).

During operation, the integrated circuit activates a communicationchannel having a carrier frequency in a radio in the interface circuitto listen for the advertising frame of interest (operation 610) from theother electronic device during the scan window having the predefinedduration. If the advertising frame of interest is received from theother electronic device (operation 612), the integrated circuitterminates the listening (operation 614) before the predefined durationhas expired and, using the communication channel in the radio, transmitsthe connect request (operation 614) to the other electronic device toestablish the connection with the other electronic device. Otherwise,the integrated circuit takes no action (operation 616) so that thescanning continues until the predefined duration has expired.

In some embodiments, the advertising frame received in operation 612includes an encoded address (such as the randomly generated addressdiscussed previously with reference to FIG. 1). If the electronic deviceand the other electronic device were previously paired (i.e., if theelectronic device and the other electronic device were previouslyconnected), the electronic device may have information specifying thehash function and/or the random number generator, which may be used todetermine an actual address of the other electronic device (such as theMAC address). This actual (physical) address may allow the electronicdevice to determine if the advertising frame (and, thus, the otherelectronic device) is of interest.

After the connection is established, the electronic device may attemptto access services supported by the other electronic device, as well asassociated data. However, before the electronic device can access thisinformation, it typically must obtain the information specifying theservices supported by the other electronic device and the details of howthis data is arranged or stored in the other electronic device (which issometimes referred to as a ‘remote data structure’). This information isoften obtained by transmitting a set of request messages from theelectronic device to the other electronic device, and receiving acorresponding set of response messages from the other electronic deviceto the electronic device. Typically, the sequence of request andresponse messages can take more than a second to communicate. This delaycan be frustrating to a user of the electronic device, may degrade theuser experience, and may increase power consumption.

These problems can be addressed by caching the remote data structure.However, the representation of the remote data structure may beincomplete, and obtaining all of this information may be undulytime-consuming.

In a more efficient and tractable approach (which is sometimes referredto as an ‘attribute protocol’), the electronic device may cache theresults of discovery queries or requests, as well as the type andparameters of the discovery request. In this way, the partial cache willindicate whether the discovery was complete or partial, and whether thedesired information was obtained.

This communication technique is shown in FIG. 7, which presents a flowdiagram illustrating a method 700 for communicating between electronicdevices, which may be performed by electronic device 900 (FIG. 9) orintegrated circuit 1000 (FIG. 10) (which may be included in electronicdevice 900 in FIG. 9). During operation, the electronic device transmitsa request packet to the other electronic device with a discovery request(operation 710). Moreover, the electronic device stores informationspecifying the discovery request (operation 712). If a response packetwith an answer to the discovery request is received from the otherelectronic device (operation 714), the electronic device storesadditional information included in the answer (operation 716), where theadditional information specifies a position in an information hierarchyin the other electronic device and a data format associated with theposition. Otherwise, no additional information is stored (operation718).

Note that the position in the hierarchy may include a service, and thedata format may include: a start position, an end position, and anidentifier. Alternatively or additionally, the position in the hierarchymay include a characteristic associated with a service, and the dataformat may include: a start position, an end position, a permission, andan identifier. However, the stored information may exclude one or moredata value(s) at the position in the hierarchy, such as charactervalues.

By partially caching the information and the additional information, theelectronic device may significantly reduce the number of request andresponse messages, and thus the delay and the power consumption, whenthe electronic device subsequently accesses data in the informationhierarchy. In particular, while obtaining the stored additionalinformation is time-consuming a first time there is a connection betweenthe electronic device and the other electronic device, this discoveryprocess (including the request messages and the response messages) mayonly need to be performed once. Subsequently, when a connection isestablished between the electronic device and the other electronicdevice, the electronic device already knows the details of theinformation hierarchy (i.e., the data structure) in the other electronicdevice, and can immediately request (within a couple of hundredmilliseconds) desired information or data, such as a character value ata position in the data structure.

For example, the other electronic device may be an exercise monitor thatstores a heart rate of a user. This exercise monitor may offer a set ofservices, such as service S1 (such as heart-rate monitor), service S2,and service S3. Each of these services may have a start position in theinformation hierarchy, such as a flat map (or, more generally, a datastructure), an end position in the flat map, and an identifier.Moreover, service S1 may have associated characteristics, such as beatsper minute C1, amplitude C2, and sensor location C3, and correspondingcharacter values (or data).

If the electronic device transmits one or more discovery requests aboutservices S1 and S4, a software module executing in the environment ofthe electronic device may store or cache these requests. Because serviceS4 does not exist, an answer may not be received. This information mayalso be stored by the software module. (Alternatively, the absence ofadditional stored information may indicate that an answer was notreceived.) The answer to the discovery request about service S1 mayinclude start position 3 in the information hierarchy, end position 10in the information hierarchy, and an identifier.

If the electronic device is subsequently connected to the otherelectronic device again, the stored information about service S1 isavailable so it does not need to be requested again.

In some embodiments, the services on the other electronic device includeservice S0. This service may include information indicating whether thedata structure (or the information hierarchy) has changed and what waschanged. Based on this information, the electronic device may removesome or all of the cached information for the remote data structurebased on one or more caching preferences. Alternatively or additionally,the electronic device may remove some or all of the cached informationfor the remote data structure: if the connection is broken; if theaddress associated with the other electronic device cannot be reversedto the corresponding MAC address; and/or when the networking subsystemis powered off.

In some embodiments of the preceding methods, there may be additional orfewer operations. Moreover, the order of the operations may be changed,and/or two or more operations may be combined into a single operation.

We now describe embodiments of the electronic device and a system thatincludes multiple electronic devices. FIG. 8 presents a block diagramillustrating a group of electronic devices 810 wirelessly communicating.In particular, these electronic devices may wirelessly communicatewhile: discovering one another by scanning wireless channels,transmitting advertising frames on wireless channels, establishingconnections by transmitting connect requests, and/or partially cachingremote data structures.

As described further below with reference to FIGS. 9 and 10, each ofelectronic devices 810 may include subsystems, such as a networkingsubsystem, a memory subsystem and a processor subsystem. In addition,electronic devices 810 may include radios 812 in the networkingsubsystems. More generally, electronic devices 810 can include (or canbe included within) any electronic devices with the networkingsubsystems that enable electronic devices 810 to wirelessly communicatewith another electronic device. This can comprise transmittingadvertising frames on wireless channels to enable electronic devices tomake initial contact, followed by exchanging subsequent data/managementframes (such as connect requests) to establish a connection, configuresecurity options (e.g., IPSEC), etc.

As can be seen in FIG. 8, wireless signals 814 (represented by jaggedlines) are transmitted from a radio 812-1 in electronic device 810-1.These wireless signals 814 are received by radios 812-2 and 812-3 inelectronic devices 810-2 and 810-3, respectively.

In the described embodiments, processing an advertising frame in eitherof electronic devices 810-2 and 810-3 includes: receiving wirelesssignals 814 with the advertising frame; decoding/extracting theadvertising frame from received wireless signals 814 to acquire theadvertising frame; and processing the advertising frame to determineinformation contained in the advertising frame (such as the address inthe header).

Although we describe the network environment shown in FIG. 8 as anexample, in alternative embodiments, different numbers or types ofelectronic devices may be present. For example, some embodimentscomprise more or fewer electronic devices. As another example, inanother embodiment, different electronic devices are transmitting and/orreceiving frames.

FIG. 9 presents a block diagram illustrating an electronic device 900.This electronic device includes processing subsystem 910, memorysubsystem 912, and networking subsystem 914.

Processing subsystem 910 includes one or more devices configured toperform computational operations. For example, processing subsystem 910can include one or more microprocessors, application-specific integratedcircuits (ASICs), microcontrollers, programmable-logic devices, and/orone or more digital signal processors (DSPs).

Memory subsystem 912 includes one or more devices for storing dataand/or instructions for processing subsystem 910 and networkingsubsystem 914. For example, memory subsystem 912 can include dynamicrandom access memory (DRAM), static random access memory (SRAM), and/orother types of memory. In some embodiments, instructions for processingsubsystem 910 in memory subsystem 912 include: one or more programmodules or sets of instructions, which may be executed by processingsubsystem 910. Note that the one or more computer programs mayconstitute a computer-program mechanism. Moreover, instructions in thevarious modules in memory subsystem 912 may be implemented in: ahigh-level procedural language, an object-oriented programming language,and/or in an assembly or machine language. Furthermore, the programminglanguage may be compiled or interpreted, e.g., configurable orconfigured, to be executed by processing subsystem 910.

In addition, memory subsystem 912 can include mechanisms for controllingaccess to the memory. In some embodiments, memory subsystem 912 includesa memory hierarchy that comprises one or more caches coupled to a memoryin electronic device 900. In some of these embodiments, one or more ofthe caches is located in processing subsystem 910.

In some embodiments, memory subsystem 912 is coupled to one or morehigh-capacity mass-storage devices (not shown). For example, memorysubsystem 912 can be coupled to a magnetic or optical drive, asolid-state drive, or another type of mass-storage device. In theseembodiments, memory subsystem 912 can be used by electronic device 900as fast-access storage for often-used data, while the mass-storagedevice is used to store less frequently used data.

Networking subsystem 914 includes one or more devices configured tocouple to and communicate on a wired and/or wireless network (i.e., toperform network operations), including: control logic 916, an interfacecircuit 918 and an antenna 920. For example, networking subsystem 914can include a Bluetooth™ networking system, a cellular networking system(e.g., a 3G/4G network such as UMTS, LTE, etc.), a universal serial bus(USB) networking system, a networking system based on the standardsdescribed in IEEE 802.11 (e.g., a Wi-Fi networking system), an Ethernetnetworking system, and/or another networking system.

Networking subsystem 914 includes processors, controllers,radios/antennas, sockets/plugs, and/or other devices used for couplingto, communicating on, and handling data and events for each supportednetworking system. In the preceding discussion, the mechanisms used forcoupling to, communicating on, and handling data and events on thenetwork for each network system were sometimes collectively referred toas a ‘network interface’ for the network system. Note that in someembodiments, a ‘network’ between the electronic devices does not yetexist. Therefore, electronic device 900 may use the mechanisms innetworking subsystem 914 for performing simple wireless communicationbetween the electronic devices, e.g., transmitting advertising framesand/or scanning for advertising frames transmitted by other electronicdevices as described previously.

Within electronic device 900, processing subsystem 910, memory subsystem912, and networking subsystem 914 are coupled together using bus 922.Bus 922 may include an electrical, optical, and/or electro-opticalconnection that the subsystems can use to communicate commands and dataamong one another. Although only one bus 922 is shown for clarity,different embodiments can include a different number or configuration ofelectrical, optical, and/or electro-optical connections between thesubsystems.

Electronic device 900 can be (or can be included in) any electronicdevice with at least one network interface. For example, electronicdevice 900 can be (or can be included in): a desktop computer, a laptopcomputer, a server, a media player (such as an MP3 player), anappliance, a subnotebook/netbook, a tablet computer, a smartphone, acellular telephone, a piece of testing equipment, a network appliance, aset-top box, a personal digital assistant (PDA), a toy, a controller, adigital signal processor, a game console, a computational engine withinan appliance, a consumer-electronic device, a portable computing device,a personal organizer, and/or another electronic device.

Although specific components are used to describe electronic device 900,in alternative embodiments, different components and/or subsystems maybe present in electronic device 900. For example, electronic device 900may include one or more additional processing subsystems 910, memorysubsystems 912, and/or networking subsystems 914. Additionally, one ormore of the subsystems may not be present in electronic device 900.Moreover, in some embodiments, electronic device 900 may include one ormore additional subsystems that are not shown in FIG. 9. For example,electronic device 900 can include, but is not limited to, a displaysubsystem for displaying information on a display, a data collectionsubsystem, an audio and/or video subsystem, an alarm subsystem, a mediaprocessing subsystem, and/or an input/output (I/O) subsystem. Also,although separate subsystems are shown in FIG. 9, in some embodiments,some or all of a given subsystem can be integrated into one or more ofthe other subsystems in electronic device 900.

Moreover, the circuits and components in electronic device 900 may beimplemented using any combination of analog and/or digital circuitry,including: bipolar, PMOS and/or NMOS gates or transistors. Furthermore,signals in these embodiments may include digital signals that haveapproximately discrete values and/or analog signals that have continuousvalues. Additionally, components and circuits may be single-ended ordifferential, and power supplies may be unipolar or bipolar.

One or more circuits in portable electronic device 900 may beimplemented on an integrated circuit. This is shown in FIG. 10, whichpresents a block diagram illustrating an integrated circuit 1000, whichincludes control logic 916 and interface circuit 918.

Integrated circuit 1000 may implement some or all of the functionalityof networking subsystem 914, such as a radio. Moreover, integratedcircuit 1000 may include hardware and/or software mechanisms that areused for transmitting wireless signals from electronic device 900 (FIG.9) and receiving signals at electronic device 900 from other electronicdevices (FIG. 9). Aside from the mechanisms herein described, radios aregenerally known in the art and hence are not described in detail. Ingeneral, networking subsystem 914 (FIG. 9) and/or integrated circuit1000 can include any number of radios. Note that the radios inmultiple-radio embodiments function in a similar way to the describedsingle-radio embodiments.

In some embodiments, networking subsystem 914 (FIG. 9) and/or integratedcircuit 1000 include a configuration mechanism (such as one or morehardware and/or software mechanisms) that configures the radio(s) totransmit and/or receive on a given communication channel (e.g., a givencarrier frequency). For example, in some embodiments, the configurationmechanism can be used to switch the radio from monitoring and/ortransmitting on a given communication channel to monitoring and/ortransmitting on a different communication channel. (Note that‘monitoring’ as used herein comprises receiving signals from otherelectronic devices and possibly performing one or more processingoperations on the received signals, e.g., determining if the receivedsignal comprises an advertising frame, etc.)

While Bluetooth™ was used as an illustrative example, the describedembodiments of the communication techniques may be used in a variety ofnetwork interfaces. Furthermore, while some of the operations in thepreceding embodiments were implemented in hardware or software, ingeneral the operations in the preceding embodiments can be implementedin a wide variety of configurations and architectures. Therefore, someor all of the operations in the preceding embodiments may be performedin hardware, in software or both.

In the preceding description, we refer to ‘some embodiments.’ Note that‘some embodiments’ describes a subset of all of the possibleembodiments, but does not always specify the same subset of embodiments.

The foregoing description is intended to enable any person skilled inthe art to make and use the disclosure, and is provided in the contextof a particular application and its requirements. Moreover, theforegoing descriptions of embodiments of the present disclosure havebeen presented for purposes of illustration and description only. Theyare not intended to be exhaustive or to limit the present disclosure tothe forms disclosed. Accordingly, many modifications and variations willbe apparent to practitioners skilled in the art, and the generalprinciples defined herein may be applied to other embodiments andapplications without departing from the spirit and scope of the presentdisclosure. Additionally, the discussion of the preceding embodiments isnot intended to limit the present disclosure. Thus, the presentdisclosure is not intended to be limited to the embodiments shown, butis to be accorded the widest scope consistent with the principles andfeatures disclosed herein.

What is claimed is:
 1. An electronic device, comprising: an antenna; aninterface circuit coupled to the antenna, the interface circuitcomprising a radio; and control logic coupled to the interface circuit,wherein the control logic and the interface circuit are configured to:activate the radio to monitor for an advertising frame from an otherelectronic device during a scan window; and when the advertising frameis received from the other electronic device before the scan window hasexpired, terminate the monitoring before the scan window has expired;and use the radio to transmit a connect request to the other electronicdevice.
 2. The electronic device of claim 1, wherein a connection haspreviously been established with the other electronic device.
 3. Theelectronic device of claim 1, wherein the advertising frame includes anencoded address; and wherein the control logic is further configured todetermine an actual address of the other electronic device.
 4. Theelectronic device of claim 3, wherein the encoding is based at least inpart on a pseudorandom number.
 5. The electronic device of claim 1,wherein the interface circuit in the electronic device is configured toperform the monitoring and transmitting in accordance with a Bluetooth™standard.
 6. The electronic device of claim 1, wherein the connectrequest is transmitted before an initiation state of the electronicdevice.
 7. An integrated circuit, comprising: an interface circuitcomprising a radio; and control logic; wherein the control logic and theinterface circuit are configured to: activate the radio to monitor foran advertising frame from an other electronic device during a scanwindow; and when the advertising frame is received from the otherelectronic device before the scan window has expired, terminate themonitoring before the scan window has expired; and use the radio totransmit a connect request to the other electronic device.
 8. Theintegrated circuit of claim 7, wherein a connection has previously beenestablished with the other electronic device.
 9. The integrated circuitof claim 7, wherein the advertising frame includes an encoded address;and wherein the control logic is further configured to determine anactual address of the other electronic device.
 10. The integratedcircuit of claim 9, wherein the encoding is based at least in part on apseudorandom number.
 11. The integrated circuit of claim 7, wherein theinterface circuit in the electronic device is configured to perform themonitoring and transmitting in accordance with a Bluetooth™ standard.12. The integrated circuit of claim 7, wherein the connect request istransmitted before an initiation state of the electronic device.
 13. Amethod for operating an electronic device that comprises control logicand an interface circuit comprising a radio, the method comprising: bythe control logic and the interface circuit, performing operations for:activating the radio to monitor for an advertising frame from an otherelectronic device during a scan window; and when the advertising frameis received from the other electronic device before the scan window hasexpired, terminating the monitoring before the scan window has expired;and using the radio to transmit a connect request to the otherelectronic device.
 14. The method of claim 13, wherein a connection haspreviously been established with the other electronic device.
 15. Themethod of claim 13, wherein the advertising frame includes an encodedaddress; and wherein the method further comprises determining an actualaddress of the other electronic device.
 16. The method of claim 15,wherein the encoding is based at least in part on a pseudorandom number.17. The method of claim 13, wherein the monitoring and transmitting areperformed in accordance with a Bluetooth™ standard.
 18. The method ofclaim 13, wherein the connect request is transmitted before aninitiation state of the electronic device.